1. Field of Invention
This invention relates to hand held devices for separating granular materials according to relative specific gravities, with or without the use of a liquid medium, especially those used in gold panning to recover precious metals from native granular materials.
2. Description of Prior Art
The object of panning for gold is to retrieve as much gold as possible, in any given time period from granular materials such as gravel, sand or clay without losing any gold in the process, especially "flour gold" which constitutes the majority of gold panned. "Flour gold" is fine pieces of gold that are so small that they are almost undetectable with the unaided eye.
During the past 200 years or more many problems associated with gold panning have been recognized and some attempts have been made to solve them. These problems can be lumped into general areas such as:
1) SPEED:
a) Panning time can be reduced by simply not processing most of the waste materials. Gold particles are usually small and much of the waste material is in large pieces. Prescreening of your raw supply of granular materials can eliminate 80% to 95% of waste before panning begins. Screening of materials in the gold pan as suggested by LITRAP (U.S. Pat. No. 4,289,241--Sep. 15, 1981) and REMIAS (U.S. Pat. No. 5,190,158--Mar. 2, 1993) is not only counterproductive, but requires much more expensive equipment to accomplish.
b) The process of gold panning involves repeated cycles of shaking the pan to settle gold toward the bottom followed by tilting the pan then washing waste materials off the top and out of the pan. Because of a declining volume of materials left in the pan, each successive wash cycle removes a smaller volume of waste material from the pan. Each time you finish a shaking cycle you must allow the materials to settle into a solid mass before starting the wash cycle. More time and more energy are required to shake the materials loose again to restart the concentration process. Materials shift during the wash cycle thereby destroying part of the gain made during the previous shaking cycle.
The farther you go, the slower the process becomes. For this reason, experienced panners save time by working down to a certain level of concentration then collecting concentrates from many pans into a second device before doing the final separation of gold from the remaining waste materials.
Inventor LITRAP (U.S. Pat. No. 4,289,241--Sep. 15, 1981) by concentrating on the ability to do final gold separation in his pan, sacrificed speed and efficiency and also created other problems.
c) The volume of gold in a pan of granular materials is usually less than one tenth of one percent of total pan volume. It does not take long to settle the gold to the bottom of the pan but once it gets there it is not very concentrated and it still has more than 99 percent waste materials sitting on top of it.
Much time and energy is used while trying to get the gold all together in one place in the pan's bottom and in washing the waste material out of the pan. As the total volume of material in the pan decreases, it becomes more difficult to wash waste material out without also losing gold.
Some inventors have tried to solve the concentration problem by creating recesses, channels, traps, pockets, indentations or some other kind of depression in the bottom of the pan where the depression constitutes only a small fraction of the surface area of the pan bottom. If all the gold could be moved into the depression then it would be much more concentrated than when it was spread all over the pan's bottom.
Inventions with bottom depressions include:
Sletcher: U.S. Pat. No. 585,989: Jul. 6, 1897 PA1 Ord: U.S. Pat. No. 1,064,853: Jun. 17, 1913 PA1 Ord: U.S. Pat. No. 1,064,854: Jun. 17, 1913 PA1 Ord: U.S. Pat. No. 1,419,405: Jun. 13, 1922 PA1 Ord: U.S. Pat. No. 1,444,752: Feb. 6, 1923 PA1 Nicolai: U.S. Pat. No. 1,948,797: Jul. 25, 1932 PA1 Streng: U.S. Pat. No. 2,630,226: Jan. 10, 1951 PA1 Lawrence et al: U.S. Pat. No. 3,899,418: Aug. 12, 1975 PA1 Legg: U.S. Pat. No. 4,273,648: Jun. 16, 1981 PA1 Morgan: U.S. Pat. No. 4,319,994: Mar. 16, 1982 PA1 Gordon Jr.: U.S. Pat. No. 4,400,269: Aug. 23, 1983 PA1 Kendall, Sr.: U.S. Pat. No. 37,758: Feb. 24, 1863 PA1 Ord: U.S. Pat. No. 1,292,364: Jan. 21, 1919 PA1 Nicolai: U.S. Pat. No. 1,948,797: Jul. 25, 1932 PA1 Streng: U.S. Pat. No. 2,630,226: Jan. 10, 1951 PA1 Legg: U.S. Pat. No. 4,273,648: Jun. 16, 1981 PA1 Morgan: U.S. Pat. No. 4,319,994: Mar. 16, 1982 PA1 Brock: U.S. Pat. No. 32,115: Apr. 23, 1861 PA1 Sletcher: U.S. Pat. No. 585,989: Jul. 6, 1897 PA1 Moore: U.S. Pat. No. 634,120: Oct. 3, 1899 PA1 Collins: U.S. Pat. No. 646,382: Mar. 27, 1900 PA1 Tobin: U.S. Pat. No. 664,066: Dec. 18, 1900 PA1 Campbell: U.S. Pat. No. 667,969: Feb. 12, 1901 PA1 White: U.S. Pat. No. 923,392: Jun. 1, 1909 PA1 Ryan: U.S. Pat. No. 1,966,359: Dec. 7, 1932 PA1 Danills: U.S. Pat. No. 1,972,645: Oct. 6, 1932 PA1 Smith: U.S. Pat. No. 3,059,776: Oct. 23, 1962 PA1 Stephenson: U.S. Pat. No. 3,855,119: Dec. 17, 1974 PA1 Lagel: U.S. Pat. No. 4,162,969: Jul. 31, 1979 PA1 Litrap: U.S. Pat. No. 4,289,241: Sep. 15, 1981 PA1 Gordon Jr.: U.S. Pat. No. 4,400,269: Aug. 23, 1983 PA1 Ottrock: U.S. Pat. No. 4,671,868: Jun. 9, 1987 PA1 Remias: U.S. Pat. No. 5,190,158: Mar. 2, 1993 PA1 Remais: U.S. Pat. No. 5,190,158: Mar. 2, 1993 PA1 Gordon Jr.: U.S. Pat. No. 4,400,269: Aug. 23, 1983 PA1 Litrap: U.S. Pat. No. 4,289,241: Sep. 15, 1981 PA1 a) The designed improvements did not perform as well as anticipated. PA1 b) The designed improvements created more problems than they solved. PA1 c) The improved designs were too expensive to produce at a price acceptable to the marketplace. PA1 1) providing a gold pan that requires only one continuous motion from start to finish to achieve maximum concentration in the pan. PA1 2) providing a gold pan that does not require stopping and starting of the concentration process. PA1 3) providing a gold pan that does not require a separate motion or step for incremental washing of waste from the pan. PA1 4) providing a gold pan with an internal design that accelerates the movement of gold particles into the desired area of concentration. PA1 5) providing a gold pan with a desired area of concentration whose cubic volume is less than one tenth of one percent of the cubic volume of the entire pan. PA1 6) providing a gold pan that holds the gold particles in the desired area of concentration once they get there and does not allow them to spill out again. PA1 7) providing a gold pan which can process several loads of granular material before the gold is removed. PA1 8) providing a gold pan where the gold can be removed through a bottom opening without first washing the waste materials off the concentrates. PA1 9) providing a gold pan whose internal design creates smooth laminar flow and allows aggressive panning action without risk of losing fine gold particles. PA1 10) providing a gold pan whose internal design promotes rapid concentration with smooth, straight, non-turbulent laminar flow of materials and no wasted energy. PA1 11) Providing a gold pan that achieves higher concentration of gold in the pan. PA1 12) Provide a gold pan where 100% of all internal surface areas slope downward and inward toward the desired area of concentration and nothing impedes the movement of gold particles toward that area.
None of these inventions with bottom depressions have achieved commercial success perhaps because they did not perform as anticipated. There are two reasons for poor performance.
First, when the pan is first filled the depression fills quickly with mostly waste materials. After the gold particles settle to the bottom the pan is shaken from side to side to try and move the pieces of gold to the depression area. Gold can move around the pan bottom many times and never pass over the depression. Even when it passes over the area of the depression it is not likely to enter the depression because the depression is already packed solid with mostly heavy waste materials. The panner can't see where the gold particles are.
Second, even when gold particles enter the depression it is likely they will not stay there. As the panner tilts the pan to wash out waste materials everything in the pan shifts and gold is very likely to spill out of the depression again. Contrary to expectations the depression actually seems to be a hindrance rather than a help in concentration.
Johnson: U.S. Pat. No. 799,059: Sep. 12, 1905 utilized a round pan that was conical in shape. In the tip of the cone was a copper plate. The object was to coat the copper plate with mercury which absorbed fine gold but could not hold larger nugget pieces of gold. Although the cone shape made it easier to get the gold into a small area, the round shape still created turbulence with the potential for loss of gold. The problems of washing off waste materials and recovering all the gold is still there and perhaps even complicated by the mercury coated plate.
d) Some inventors have attempted to resolve the need to wash waste materials out of the pan by providing a means for removing gold concentrates through the bottom of the pan.
Inventions with means for bottom removal include:
None of these inventions with bottom removal have achieved commercial success for three reasons.
First, as the prior discussion has shown, noone has been able to overcome the problems created by the pan bottom and effectively concentrate the gold in a small area above the pan bottom opening.
Second, prior bottom opening devices were complicated and did not function as well as anticipated.
Third, prior bottom opening devices were too expensive to manufacture and could not be produced at a price acceptable to the marketplace. A simpler opening and a seal that could be pulled out and pressed in without the need for screws, bolts, pins, hinges, etc. would have been a significant improvement to any of these designs.
e) Earlier pans had smooth sides and bottoms. If a panner was too aggressive in shaking the pan there was a risk of losing gold by having it slide up the side and over the top of the pan.
Several inventors have designed indentations, riffles, ridges, corrugations and other irregular shapes into the sides and bottoms of their pans. They include:
Most inventors use the riffles, etc. to retard the movement of gold up the sides of the pan during the shaking, tilting and washing cycles. Some are to provide supports for various screening inserts for the pans. Gordon Jr. (U.S. Pat. No. 4,400,269: Aug. 23, 1983) and Remias (U.S. Pat. No. 5,190,158: Mar. 2, 1993) used some of their beads, riffles, risers, and ribs to create "turbulence" for breaking up granular materials.
Turbulence is counterproductive because it consumes energy with no offsetting benefits; it can cause gold to move up in the pan rather than down toward the desired area of concentration and it can dislodge fine gold, allowing it to be washed out of the pan along with waste mateirals.
Although most of these riffle, ridge, etc. designs have some beneficial effects when the pan is full of granular materials there are also some unrecognized disadvantages.
These designed features that resist the movement of gold up the sides and out of the pan also resist the movement of waste materials up and out of the pan, especially when the volume of materials in the pan becomes small. During the final stages of the concentrating process it becomes more difficult to wash the fine heavy particles of waste material out of the pan without also losing gold. This forces the panner to slow down the process, not only wasting time, but also wasting energy. There is a continuing need to stop washing and shake the gold back to the bottom of the pan again.
When the volume of materials remaining in the pan is low there is not enough to cover the riffles from end to end and there is no means to spread the granular material level along the riffles. Water tends to flow around the edges of the granular materials and over the riffles creating many points of turbulence that dislodge fine gold and washes it out of the pan.
2) SKILL: There are world championship competitions held to see who has developed the best skills of gold panning. Many beginning panners have finished a pan of materials only to find no gold, because they accidently washed it all out during the panning process. Professional panners will tell you that they have special little movements they use that others do not recognize. Some partime panners pan for weeks, months or even years before becoming proficient.
3) FLOATING GOLD: One process for separating gold from finely ground materials is to introduce water and an oily substance into the material then blow air bubbles that move up to the surface. Gold has a great affinity for oily substances like the oil on your hand that produces fingerprints and handprints.
The oil not only clings to the gold, thereby reducing its relative specific gravity, but it also enhances the strength of the surface tension of water, especially inside the bubbles. The fine gold, coated with oil, is carried by the bubbles to the surface where it can be skimmed off and refined.
Many experienced panners have looked into the bottom of their pan and have seen small pieces of gold called colors. After swirling the water and pouring it off, the colors were gone from the pan. Some have even swirled their pans and before pouring the water off they have seen the small pieces of gold floating on the surface like chips of wood. The first time you see it, it is difficult to believe.
All prior art practically guarantees that you will touch the inside of the gold pan with your fingers thereby leaving oil to attach itself to fine gold particles. Special movements of the pan either during shaking or during the washing cycles require a grip on the inside of the pan. Gordon Jr. (U.S. Pat. No. 4,400,269--Aug. 23, 1983) even designed his pan for the thumb to be gripping inside the pan from start to finish. Remias (U.S. Pat. No. 5,190,158: Mar. 2, 1993) designed his pan to also serve as a shovel by gripping either end or either side. Litrap (U.S. Pat. No. 4,289,241: Sep. 15, 1981) recommends using your hands to pick rocks and pebbles out of the pan and using your fingers to stir the materials in the pan. These three designers are practically guaranteeing some loss of fine gold.
4) INTERNAL FLOW DESIGN:
a) When gold is being concentrated in granular materials, each individual particle must move from a widely dispersed position to an area of high concentration, usually somewhere in the lowest part of the pan. If the granular materials are sitting at rest, no movement of the gold particles can occur.
If the granular materials are shaken sufficiently they will become "fluidized". In this state, each particle can move independently of adjacent particles and the gold particles being heavier will tend to migrate downward until they come in contact with a surface of the pan. The deeper the gold travels, the harder it becomes for it to move because of the weight of materials on top of it.
If a particle of gold comes to rest on a level surface its progress toward the desired area of concentration is stopped and much energy is required to shake the pan hard enough to move the particle sideways because of the weight of material on top of it.
If a particle of gold comes to rest on a downward sloping surface then only a small amount of energy needs to be spent to encourage it to progress toward the desired area of concentration. If the particle of gold bumps into any obstruction as it moves along the downward sloping surface, additional energy is required to pass this obstruction on the way to the desired area of concentration.
Pan bottoms as well as shelf areas, supports, beads, ridges, risers, steps, ribs, valleys, etc. impede the progress of gold particles toward the desired area of concentration. They require the expenditure of extra energy and even then it is difficult to control the direction of movement of the gold particles.
Pan designs that rely heavily on these internal riffle designs include:
b) As mentioned above, the gold particles can only progress toward the desired area of concentration when they are in a fluidized state. In gold panning, whether you are using a liquid medium or not, this is accomplished by shaking the pan so that the materials move back and forth across the pan or around the pan in a motion called laminar flow.
Laminar flow is occuring when the materials at or near the surface are moving easier and farther than the materials in the lower levels. Each successive lower layer moves slower and less farther than the layer above it. If the pan is not being shaken hard enough, the lowermost levels may not be fluidized at all and therefore no further concentration is occuring there.
The best laminar flow occurs when all the materials in the pan are moving in the same direction and are free of turbulence. This is when the greatest concentration of gold particles is occuring with the least expenditure of energy.
Pans with curved surfaces and with riffles, grooves, notches, holes and troughs interfere with laminar flow because they create turbulence. Turbulence not only is counterproductive to concentrating as shown several times in the preceding writing but it also consumes extra energy with no offsetting benefit. Sidewalls that open or converge either up and down or from end to end cause pinching and turbulence.
Parallel, flat vertical sides provide an ideal structure for turbulence-free, laminar flow. Gordon Jr. in U.S. Pat. No. 4,400,269: Aug. 23, 1983 used substantially vertical sides for a different reason. However, the necessity of thumb holes and pouring troughs which he designed into these sides to overcome some problems created yet other new problems. Not only do they introduce oil into the materials which causes the "floating gold" problem mentioned above, but they also create turbulence which greatly interferes with smooth laminar flow.
5) ENERGY: Gold panning is a very tiring and some might call a backbreaking activity. Designs that save time and energy allow the panner to retrieve more gold by processing more materials in a given period of time or work longer without getting exhausted.
6) COMMERCIAL SUCCESS: Over the past 150 years or longer several problems have been recognized in gold panning and many designs have been proposed to solve them. Yet today most of all gold pans in daily use are almost identical to the ones available 200 years ago. They are round, have sloping sidewalls and a flat bottom. The only improvement that remains is that the most popular round pan in use today has some large riffles in only one section of it's sloping sidewalls.
There are three basic reasons why designed improvements have not lasted: